Stretch composites and methods of making the composite

ABSTRACT

A stretch composite having one or more elastomeric members disposed on at least one region of an extensible fibrous substrate to provide stretch properties to a targeted region of the substrate. The composite has been incrementally stretched to at least partially break up the structure of the substrate in order to reduce its resistance to stretch. The stretch composites are useful for disposable and durable articles, such as disposable absorbent articles including diapers, pull-on diapers, training pants, incontinence briefs, catamenial garments, baby bibs, and the like, and durable articles like garments including sportswear, outerwear and the like. The present invention also relates to methods of forming such stretch composites.

CROSS REFERENCE TO RELATED APPLICATIONS

This patent application is a continuation of U.S. application Ser. No.10/288,126, filed Nov. 5, 2002; which claims the benefit of U.S.Provisional Application No. 60/337,804, filed Nov. 5, 2001; and U.S.Provisional Application No. 60/400,282, filed on Jul. 31, 2002.

FIELD OF THE INVENTION

A stretch composite having one or more elastomeric members disposed onat least one region of an extensible fibrous substrate to providestretch properties to a targeted region of the substrate. The compositehas been incrementally stretched to at least partially break up thestructure of the substrate in order to reduce its resistance to stretch.The stretch composites are useful for disposable and durable articles,such as disposable absorbent articles including diapers, pull-ondiapers, training pants, incontinence briefs, catamenial garments, babybibs, and the like, and durable articles like garments includingsportswear, outerwear and the like. The present invention also relatesto methods of forming such stretch composites.

BACKGROUND OF THE INVENTION

Disposable absorbent products, such as diapers, training pants,incontinence articles typically include stretchable materials, such aselastic strands, in the waist region and the cuff regions to provide asnug fit and a good seal of the article. Pant-type absorbent articlesfurther include stretchable materials in the side portions for easyapplication and removal of the article and for sustained fit of thearticle. Stretchable materials have also been used in the ear portionsfor adjustable fit of the article.

There are various approaches to provide desirable elastic properties inthose areas. Stretchable materials may be films or nonwoven fibrous websmade of elastomeric materials. Typically, such materials are stretchablein any direction. However, because the films or webs are made entirelyof elastomeric materials, they are relatively expensive, and they tendto have more drag on skin surface, resulting in discomforts to thewearer of the article. Sometimes, the stretchable films are laminated toone or more layers of nonwoven webs. Since typical nonwoven webstypically are made of thermoplastic fibers, they have very limitedstretchability and, the resulting laminates provide considerableresistance to stretch. It is necessary to reduce this resistancesubstantially in order to make functional stretch laminates.

Other approaches to make stretchable materials are also known,including: stretch-bonded laminates (SBL) and necked-bonded laminates(NBL). Stretch bonded laminates are made by stretching the elasticstrands in the machine direction (MD), laminating it to one or morenonwoven substrates while it is in the stretched state, and releasingthe tension in the elastic strands so that the nonwovens gather and takeon a puckered shape. Necked-bonded laminates are made by firststretching the nonwoven substrate in the machine direction such that itnecks (i.e., reduces its dimension) at least in the cross machinedirection (CD), then bonding the elastic strands to the substrate whilethe substrate is still in the stretched, necked state. This laminatewill be stretchable in CD, at least up to the original width of thenonwoven before it was necked. Combinations of stretch bondings and neckbondings have also been known to deliver stretch in both MD and CDdirection. In these approaches, at least one of the components is in atensioned (i.e., stretched) state when the components of the laminatesare joined wherein.

Zero strain stretch laminates are also known. The zero strain stretchlaminates are made by bonding the elastomer to the nonwoven while bothare in an unstrained state. The laminates are then incrementallystretched to impart the stretch properties. The incrementally stretchedlaminates are stretchable only to the extent afforded by thenon-recovered (i.e., residual) extensibility of the laminate. Forexample, U.S. Pat. No. 5,156,793, issued to Buell et al., discloses amethod for incrementally stretching the elastomeric-nonwoven laminateweb, in a non-uniform manner, to impart elasticity to the resultinglaminate.

In all the approaches above, stretch laminates are made separately. Thestretch laminates must be cut into the appropriate size and shape, thenadhesively attached to the desired location in the product in a processsometimes referred as the “cut-and-slip” process. Because of thedifferent stretch properties required for different elements of theproduct, it is necessary to make a variety of laminates having differentstretchability and cut the laminates to different sizes and shapes.Several cut and slip units may be needed to handle the differentstretchability of the stretch laminates and to attach them to differentlocations of the product. As the number of cut-and-slip units and/orsteps multiplies, the process quickly becomes cumbersome andcomplicated.

Based on the foregoing, it is desirable to have a cost effective stretchcomposite having elastomeric materials disposed only in specific areasin specific amount for stretchability to provide desired in-use benefitsof an article, such as sealing, gasketing, containing, body-conforming,or fit. It is also desirable to have a stretch composite deliveringstretchability in targeted areas among discrete, spaced apart componentsof the article. It is further desirable to have stretch compositesdelivering targeted stretchability locally (i.e., within a component ofthe article).

Moreover, it is desirable to have an efficient and cost effectiveprocess that does not involve multi-steps and/or multi-units and thatdelivers stretch properties to various portions of the absorbentarticle. Such process for making the above stretch composites isdesirable because it has total flexibility that allows for controlleddeposition of different types and/or amount of elastomeric materials tothe targeted areas only. Such process is also desirable because ittailors the delivery of stretchability and resistance to stretch invarious portions of a product to deliver improved fit and comfort to thewearer.

SUMMARY OF THE INVENTION

The present invention relates to a stretch composite comprising anextensible fibrous substrate having at least one elastomeric memberdisposed on at least a portion of the substrate to form an elasticizedregion, wherein the elastomeric member has an average width greater thanabout 0.2 mm, a melt viscosity of from about 1 to about 150 Pa·s,measured at 175° C. and 1 s⁻¹; an elasticity at least about 50 N/m; anda percent set of less than about 20%.

The stretch composite may be used for portions of an absorbent articleto provide desired benefits including better fit, improved comfort,lower forces to put on and/or take off the article. The portions of theabsorbent article that desire stretchability typically include, but arenot limited to, the waist regions, the leg cuffs, side panels, earportions, topsheet, outercover and the fastener system.

All documents cited are, in relevant part, incorporated herein byreference; the citation of any document is not to be construed as anadmission that it is prior art with respect to the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

While the specification concludes with claims particularly pointing outand distinctly claiming the subject matter which is regarded as thepresent invention, it is believed that the invention will be more fullyunderstood from the following description taken in conjunction with theaccompanying drawings, in which:

FIG. 1 is a schematic illustration of a representative process of thepresent invention;

FIG. 2A is a perspective view of one embodiment of a pant type diapercontaining the stretch composite of the present invention;

FIG. 2B is a perspective view of another embodiment of a diaper in itsin-use configuration containing the stretch composite of the presentinvention;

FIG. 3A is a plan view of an exemplary stretch composite with first andsecond elastomeric compositions applied as rectilinear stripes inparallel patterns;

FIG. 3B is a plan view of an exemplary stretch composite with firstelastomeric composition applied as rectilinear stripes in a parallelpattern and second elastomeric composition applied as rectilinearstripes in a non-parallel pattern;

FIG. 3C is a plan view of an exemplary stretch composite with first andsecond elastomeric compositions applied as rectilinear stripes innon-parallel patterns;

FIG. 4 is an enlarged perspective view of a primary operation of thepresent invention which includes applying elastomeric members to asubstrate and joining with another substrate;

FIG. 5 is an enlarged perspective view of an optional secondaryoperation of the present invention which uses interengaging formingrolls to incrementally stretching the composite preform;

FIG. 6 is an enlarged perspective view of a pair of closely-spacedforming rolls each having alternating and interengaging peripheral teethand grooves; and

FIG. 7 an enlarged fragmentary cross-sectional view showing the tipportions of the teeth of the interengaging forming rolls with a webmaterial positioned between the rolls and spanning and in contact withthe tips of adjacent teeth.

DETAILED DESCRIPTION OF THE INVENTION

The term “disposable” as used herein refers to describe products whichgenerally are not intended to be laundered or otherwise restored orextensively reused in their original function, i.e., preferably they areintended to be discarded after about 10 uses or after about 5 uses orafter about a single use. It is preferred that such disposable articlesbe recycled, composted or otherwise disposed of in an environmentallycompatible manner.

The term “durable” as used herein refers to describe products whichgenerally are intended to be laundered or otherwise restored orextensively reused in their original function, i.e., preferably they areintended to be used more than about 10 times.

The term “disposable absorbent article” as used herein refers to adevice that normally absorbs and retains fluids. In certain instances,the phrase refers to devices that are placed against or in proximity tothe body of the wearer to absorb and contain the excreta and/or exudatesdischarged from the body, and includes such personal care articles asfastened diapers, pull-on diapers, training pants, swim diapers, adultincontinence articles, feminine hygiene articles, and the like. In otherinstances, the term also refers to protective or hygiene articles, forexample, bibs, wipes, bandages, wraps, wound dressings, surgical drapes,and the like.

The term “web” as used herein refers to any continuous material,including a film, a nonwoven fabric, a woven fabric, a foam or acombination thereof, or a dry lap material including wood pulp, and thelike, having a single layer or multiple layers.

The term “substrate” as used herein refers to any material, including afilm, a nonwoven web, a woven web, a foam or a combination thereof, or adry lap material including wood pulp, cellulosic materials, derivatizedor modified cellulosic materials, and the like, having a single layer ormultiple layers.

The term “fibrous substrate” as used herein refers to a materialcomprised of a multiplicity of fibers that could be either a natural orsynthetic material or any combination thereof. For example, nonwovenmaterials, woven materials, knitted materials, and any combinationsthereof.

The term “nonwoven” as used herein refers to a fabric made fromcontinuous filaments and/or discontinuous fibers, without weaving orknitting by processes such as spun-bonding, carding and melt-blowing.The nonwoven fabric can comprise one or more nonwoven layers, whereineach layer can include continuous filaments or discontinuous fibers.Nonwoven can also comprise bi-component fibers, which can haveshell/core, side-by-side, or other known fiber structures.

The term “elastomer” as used herein refers to a polymer exhibitingelastic properties.

The term “elastic” or “elastomeric” as used herein refers to anymaterial that upon application of a biasing force, can stretch to anelongated length of at least about 160 percent of its relaxed, originallength, without rupture or breakage, and upon release of the appliedforce, recovers at least about 55% of its elongation, preferablyrecovers substantially to its original length that is, the recoveredlength being less than about 120 percent, preferably less than about 110percent, more preferably less than about 105 percent of the relaxedoriginal length.

The term “inelastic” refers herein to any material that does not fallwithin the definition of “elastic” above.

The term “extensible” or “inelastically elongatable” refers herein toany material that upon application of a biasing force to stretch beyondabout 110 percent of its relaxed original length will exhibit permanentdeformation, including elongation, rupture, breakage, and other defectsin its structure, and/or changes in its tensile properties.

The stretch composite of the present invention comprises one or moreelastomeric members disposed on and at least partially penetrating aportion of an extensible fibrous substrate, which is permanentlyelongated in the finished composite. Different elastomeric members canbe disposed on spaced-apart, adjacent or overlapping portions of thesubstrate to deliver different properties, especially differentelasticity. The stretch composite can be made in situ as a portion of anarticle by the present process to form a desired article having astretch laminate therein. The in-situ process eliminates additionalprocessing steps, such as cutting, shaping, and bonding. In the processof the present invention, the expensive elastomeric material is usedefficiently by delivering one or more elastomeric members to the articleonly where they are needed and in the amount needed. Further, theresulting product made with the laminate and the process disclosedherein can provide improved product fit and comfort.

The elastomeric members can have varied shapes and profiles in anydirection, which result in desired variations in physical properties ofthe composite material within the elastomeric members. The planar shapein the x-y direction of the elastomeric members can be any suitablegeometrical shape defining the planar dimensions of the compositematerial, including a rectilinear outline, a curvilinear outline, atriangle, a trapezoid, a square, a parallelogram, a polygon, an ellipse,a circle, and any combination thereof. The contour profile in the zdirection of the elastomeric members can be any suitable geometric shapeincluding linear and nonlinear profiles. The variation in the dimensionin the z direction and the x-y plane can be achieved by the process ofthe present invention. Typically, the average width of individualelastomeric member is at least about 0.2 mm, preferably at least about 1mm, and more preferably at least about 2 mm. The average thickness ofindividual elastomeric member is from about 0.1 mm to about 2.5 mm,preferably from about 0.25 mm to about 2 mm, and more preferably fromabout 0.5 mm to about 1.5 mm. The average width and thickness of theelastomeric members can be determined by conventional optical microscopyor by scanning electron microscopy (according to ASTM B748) for moreprecise measurements. For some embodiments, the thickness of theelastomeric member and/or the composite can be measured under a pressureof 0.25 psi (1.7 Kpa) using a microcaliper.

The variable physical properties may include tensile strength, elasticmodulus, elasticity, conductivity, breathability (i.e., vapor and/or gaspermeability), liquid impermeability, and others. Further, uniqueinterrelationships between physical properties can be formed, forexample the ratio of modulus to density, tensile strength to density,and the like.

FIG. 2A illustrates one embodiment of an absorbent article (a pant typediaper) in an in-use configuration, at least a portion of the articlecomprises the stretch laminate of the present invention. Pant typediaper 20 may comprise a plurality of elastic components on a substrate,typically a nonwoven fibrous web, to provide specific functions for thediaper. The elastic components include elasticized cuff region 12comprising leg elastomeric members 24 for gasketing function around thelegs of the wearer; elasticized waist region 14 comprising waistelastomeric members 28 for gasketing function around the waist;elasticized side panel 15 comprising panel elastomeric members 25 foradjustable fit function around the lower torso; and chassis elastomericmembers 26 over outer cover 40 for adjustable fit function directedmainly to tummy, buttocks and/or the crotch areas and for adjusting thebreathable (i.e., substantially vapor/gas permeable and liquidimpermeable) function provided by the outer cover 40. Anotherembodiment, shown in FIG. 2B in an in-use configuration, is a disposablediaper 10 having elastic leg opening 92, elastic waist opening 94 andelastic ear portion 96 and the fastener system 80 comprising a slotmember 82 and a tab member 84, all of which can be made of the stretchcomposites of the present invention elasticated topsheet (not shown) canalso be made of the composite of the present invention.

The manufacture of these elastic components of a diaper typicallyinclude the steps of cutting from an elastomeric material (in the formof a film, a fibrous web, or a laminate) to the desired size and shape,then joining the discrete pieces of elastomeric materials to thesubstrate using known bonding methods such as adhesive, thermal,mechanical, ultrasonic bonding. In contrast, the present inventionprovides a novel process that combines the step of making of anelastomeric component and the step of joining the elastomeric componentto a substrate into a single step continuous process. A given elasticcomponent may comprise a single elastomeric member or a plurality ofelastomeric members. Moreover, in the present invention, the elastomericmembers can be applied directly onto multiple portions, corresponding todiscrete elastic components of the diaper to form the waist elastomericmembers, leg elastomeric members, etc., in one continuous process. Thepresent invention is well suited to deliver different elasticity's tomeet the different requirements of individual components of the diaper.It is also contemplated by the present invention that multipleelastomeric members having different elasticities may be applied inadjacent portions on a single element of an absorbent article. Thedifferent elasticities may be achieved by variations in meltviscosities, shapes, patterns, add-on levels, compositions, andcombinations thereof.

The elastomeric members may be applied in various shapes or patternscontinuously or intermittently. Typically, the elastomeric members maybe applied in stripes (rectilinear or curvilinear), spirals, discretedots and the like. The elastomeric members may also be applied invarious geometric or decorative shapes or figures. The various patternsmay place the elastomeric members in perpendicular, parallel and/orangled (i.e., non-parallel) positions with respect to one another, orwith respect to components of the diaper, such as a waist region, legopenings, side seams. Two elastomeric members are parallel when theyexhibit substantially uniform inter-member or lateral spacing. They arenon-parallel when they exhibit non-uniform inter-member or lateralspacing. Thus, two curvilinear elastomeric members are non-parallel ifthey have different curvatures. In another example, an elastomericmember is parallel to a waist region or a leg opening when the spacingbetween the elastomeric member and an edge of the waist region or a legopening is substantially uniform.

In one embodiment, as shown in FIG. 3A, a plurality of rectilinearstripes of a first elastomeric composition are applied in asubstantially parallel pattern along a first direction to form firstelastomeric members 301. Optionally, a plurality of rectilinear stripesof a second elastomeric composition are applied in a substantiallyparallel pattern along a second direction to form second elastomericmembers 302, the second direction being at a predetermined angle α withrespect to the first direction. The predetermined angle α ranges fromabout zero to about 90 degrees, preferably from about 1 to about 80degrees, and more preferably from about 5 to about 70 degrees. The firstand the second elastomeric compositions can be deposited on fully orpartially overlapping portions (corresponding to the same or partiallyoverlapping elastic components of the finished diaper) of the substrate.Alternatively, the first and second elastomeric compositions can bedeposited on non-overlapping (adjacent or remote) portions of thesubstrate, which correspond to distinct elastic components of thefinished diaper. Consequently, the stripes of the first and secondelastomeric compositions do not crossover.

In some embodiments, a plurality of first elastomeric members in theform of rectilinear stripes are applied in a substantially parallelpattern along a first direction, and a plurality of second elastomericmembers in the form of rectilinear or curvilinear stripes are applied ina non-parallel or angled pattern, wherein at least one, preferably aplurality of the stripes of the second elastomeric members are angled ornon-parallel to one or both adjacent stripes of the same elastomericmembers. The first and second elastomeric members may be deposited onthe same, overlapping or separate portions of the fibrous substrate.FIG. 3B illustrates one of the above embodiments wherein the firstelastomeric members are substantially parallel and rectilinear stripes303 along a first direction and the second elastomeric members arerectilinear stripes 304 which are not parallel to adjacent stripes; eachstripe of the second elastomeric members forms a predetermined angle βwith respect to the first direction. Specifically, the predeterminedangle β ranges from about zero to about 180 degrees and varies amongdifferent stripes 304. Alternatively, the first and second elastomericmembers are deposited in a non-parallel or angled pattern, and formingvarying angles between the stripes 305, 306, such as the embodimentshown in FIG. 3C.

The substrate material may be films, knitted fabric, woven fibrous websor nonwoven fibrous webs. In some embodiments, the substrates areextensible nonwoven webs made of polyolefin fibers or filaments, such aspolyethylene, polypropylene.

Suitable elastomeric compositions are applied to the substrate in afluid or fluid-like state to affect at least partial penetration intothe substrate, thus, achieving sufficient bonding between the resultingelastomeric members and the substrate such that the composite exhibitsinsubstantially delaminate in the subsequent incremental stretchingstep. The elastomeric composition may have a melt viscosity from about 1to about 150 Pa·s, preferably from about 5 to about 100 Pa·s, and morepreferably from about 10 to about 80 Pa·s, at 175° C. and 1 s⁻¹ shearrate. Such elastomeric composition is suitable for use in the presentprocesses that operate at a lower viscosity and/or lower temperaturethan the processing conditions of a typical melt extrusion and/or fiberspinning process.

Suitable elastomeric compositions comprise thermoplastic elastomersselected from the group consisting of styrenic block copolymers,metallocene-catalyzed polyolefins, polyesters, polyurethanes, polyetheramides, and combinations thereof. Suitable styrenic block copolymers maybe diblock, triblock, tetrablock, or other multi-block copolymers havingat least one styrenic block. Exemplary styrenic block copolymers includestyrene-butadiene-styrene, styrene-isoprene-styrene,styrene-ethylene/butylenes-styrene, styrene-ethylene/propylene-styrene,and the like. Commercially available styrenic block copolymers includeKRATON® from the Shell Chemical Company of Houston, Tex.; SEPTON® fromKuraray America, Inc. of New York, N.Y.; and VECTOR® from Dexco ChemicalCompany of Houston, Tex. Commercially available metallocene-catalyzedpolyolefins include EXXPOL® and EXACT® from Exxon Chemical Company ofBaytown, Tex.; AFFINITY® and ENGAGE® from Dow Chemical Company ofMidland, Mich. Commercially available polyurethanes include ESTANE® fromNoveon, Inc., Cleveland, Ohio. Commercial available polyether amidesinclude PEBAX® from Atofina Chemicals of Philadelphia, Pa. Commerciallyavailable polyesters include HYTREL® from E. I. DuPont de Nemours Co.,of Wilmington, Del.

The elastomeric compositions may further comprise processing aids and/orprocessing oils to adjust the melt viscosity of the compositions to thedesired range. They include the conventional processing oil, such asmineral oil, as well as other petroleum-derived oils and waxes, such asparafinic oil, naphthenic oil, petrolatum, microcrystalline wax,paraffin or isoparaffin wax. Synthetic waxes, such as Fischer-Tropschwax; natural waxes, such as spermaceti, carnauba, ozokerite, beeswax,candelilla, paraffin, ceresin, esparto, ouricuri, rezowax, and otherknown mined and mineral waxes, are also suitable for use herein.Olefinic or diene oligomers and low molecular weight polymers may alsobe used herein. The oligomers may be polypropylenes, polybutylenes,hydrogenated isoprenes, hydrogenated butadienes, or the like having aweight average molecular weight between about 350 and about 8000.

In one embodiment, a phase change solvent can be incorporated into theelastomeric composition to lower its melt viscosity, rendering thecomposition processable at a temperature of 175° C. or lower, withoutsubstantially compromising the elastic and mechanical properties of thecomposition. Typically, the phase change solvent exhibits a phase changeat temperatures ranging from about 40° C. to about 250° C. The phasechange solvent has the general formula:

-   -   (I) R′-Ly-(Q-L_(x))_(n−1)-Q-L_(y)-R;    -   (II) R′-L_(y)-(Q-L_(x))_(n)-R;    -   (III) R′-(Q-L_(x))_(n)-R;    -   (IV) R′-(Q-L_(x))_(n−1)-Q-L_(y)-R;    -   (V) R′-(Q-L_(x))_(n−1)-Q-R;or    -   a mixture thereof;        wherein Q may be a substituted or unsubstituted difunctional        aromatic moiety; L is CH₂; R and R′ are the same or different        and are independently selected from H, CH3, COOH, CONHR₁,        CONR₁R₂, NHR₃, NR₃R₄, hydroxy, or C1—C30 alkoxy; wherein R₁, R₂,        R₃ and R₄ are the same or different and are independently        selected from H or linear or branched alkyl from C1—C30; x is an        integer from 1 to 30; y is an integer from 1 to 30; and n is an        integer from 1 to 7. Detailed disclosure of the phase change        solvents can be found in Provisional U.S. patent application        Ser. No. 60/400,282, filed on Jul. 31, 2002.

Alternatively, the elastomeric composition may also comprise lowmolecular weight elastomers and/or elastomeric precursors of the abovethermoplastic elastomers, and optionally crosslinkers, or combinationsthereof. The weight average molecular weight of the low molecular weightelastomers or elastomeric precursors is between about 45,000 and about150,000.

Suitable elastomeric compositions for use herein are elastic withoutfurther treatment and they do not include any volatile solvents whoseboiling point is below 150° C. However, after the elastomericcomposition has been deposited onto the substrate, it may be subjectedto post-treatments to improve or enhance its elasticity and otherproperties including strength, modulus, and the like. Typically,post-treatments include drying, crosslinking, curing or polymerizing viachemical, thermal, radiation means, and combinations thereof.

The resulting elastomeric members have the following properties: (1) anelasticity (i.e., normalized load at 75% strain) of at least about 50N/m, preferably from about 50 N/m to about 300 N/m, more preferably fromabout 75 N/m to about 250 N/m, and most preferably from 100 N/m to about200 N/m; (2) a percent set of less than about 20%, preferably less thanabout 15% and more preferably less than about 10%; and (3) a stressrelaxation value of less than about 30%, preferably less than about 25%,and more preferably less than about 20%.

The elastomeric members may be applied to a specific region to achieve atotal add-on level of from about 5 to about 200 g/m², preferably fromabout 20 to about 150 g/m², and more preferably from about 50 to about100 g/m². The first and the second elasticized regions may have openareas not covered by elastomeric members ranging from about 10% to about80% of the total surface area of the region, preferably from about 20%to about 70%, and more preferably from about 40% to about 60%. Theselective depositing of elastomeric compositions uses less of thematerials than the amount would be required by the conventionallamination technology using films or sheets. The fibrous substrate incombination with the selective deposition of elastomeric members canprovide the resulting composite with lower basis weight and higherbreathability than a laminate containing a fibrous web layer and a filmor sheet layer. The fibrous substrate can further provide a soft,cloth-like feel to the skin for better wearer comfort.

Each elasticized region may have a different number of elastomericmembers disposed per unit area. The add-on level per elastomeric memberalso differs from region to region. Thus, when comparing a firstelasticized region having first elastomeric members disposed thereon anda second elasticized region having second elastomeric members disposedthereon, the ratio of the add-on level on the basis of individual firstand second elastomeric member, may range from about 1.05 to about 3,preferably from about 1.2 to about 2.5, and more preferably from about1.5 to about 2.2. Further, the first and the second elastomeric membersmay have an elasticity ratio of from about 1.1 to about 10, preferablyfrom about 1.2 to about 5, and more preferably from about 1.5 to about3.

The elastomeric members may be applied directly to the fibrous web, orindirectly transferred to the fibrous web by first deposited onto anintermediate surface. Suitable methods may include contact methods suchas gravure printing, intaglio printing, flexographic printing, slotcoating, curtain coating, and the like; and non-contact methods such asink jet printing, spraying, and the like. Each application methodoperates in a specific viscosity range, thus, a careful selection of theviscosity of the elastomeric elastomeric composition is required.Composition, temperature and/or concentration can be varies to providethe suitable viscosity for a given processing method and operatingconditions.

Temperature may be raised to lower the viscosity of the elastomericcomposition. However, high temperature may have adverse effect on thestability of the fibrous substrate, which may experience partial orlocal thermal degradation where the heated elastomeric composition isdeposited. A balance between these two effects is desirable.Alternatively, indirect/transfer methods may be used. The elastomericcomposition is heated to achieve a suitable viscosity for processing andapplied to an intermediate surface (e.g., a carrier substrate) havinggood thermal stability, which is then transferred to the fibroussubstrate to form the composite preform. The indirect/transfer methodallows for a wider range of operating temperatures because the heatedelastomeric composition is at least partially cooled when it contactsthe fibrous substrate. Thus, the indirect process may be useful forsubstrates that are thermally sensitive or unstable, such as nonwovenwebs, or substrates of low melting polymers, including polyethylene andpolypropylene. Nip pressure may be applied with nip rolls or calendarrolls to get sufficient penetration and bonding.

The non-contacting methods provide both mechanical and thermaladvantages. Since the application equipment is not in direct contactwith the substrate, there is less insult/abrasion to the structuralintegrity of the substrate. Thus, fibrous webs having lower basisweight, or lower mechanical strength can be used as the substrate. Thenon-contact methods are especially desirable for high speed processeswhere direct contact between the equipment and the substrate can applysubstantial shear and abrasive forces on the substrate, possibly causingdamages to the surface and/or the structure of the substrate. Thenon-contact methods also allow substrates with lower thermal stabilityto be used since the fluid elastomeric compositions may be partiallyair-cooled before coming into contact with the substrate. Moreover,non-contact ink jet printing process provide an additional advantage oftotal flexibility in the printed shape, pattern, etc. of the elastomericmembers without stopping the process and/or retooling the printing head.Nip pressure may also be applied, if necessary, in the non-contactprocess.

It is desirable to have the elastomeric composition at least partialpenetrates the substrate so that the resulting composite preform doesnot delaminate in the subsequent processing or manufacturing steps or inthe finished product. Additionally, such good bonding within thecomposite and/or its preform render the use of adhesives optional. Thedegree of penetration may be affected by several factors: the viscosityof the elastomeric composition when in contact with the substrate, theporosity of the substrate, the surface tension between the substrate andthe elastomeric composition. In one embodiment, the off-set gravureprinting process allows partial cooling of the elastomeric compositionbefore it contacts the fibrous substrate, thus increases its viscosityand decreases the degree of penetration into the substrate.Alternatively, the elastomeric composition may be cooled by blowingchilled air/gas onto to it prior to or while coming into contact withthe substrate. In another embodiment, the degree of penetration may beenhanced by passing the substrate/elastomeric composition through a pairof nip rolls. The temperature of the nip rolls as well as the appliednip pressure provide further control of the degree of penetration.

In another embodiment, the gravure printing method is used, whereby itis possible to vary the amount of elastomeric composition deposited indifferent portions of the substrate, thereby varying the local stretchproperties. For Example, by incorporating different depth and/or widthof grooves and lands on the gravure roll, the resulting elastomericmembers can be thicker in one area and thinner in another area. Inanother example, by changing the pattern on the gravure roll, theresulting elastomeric members can have varying the member density in theresulting composite. Furthermore, two or more gravure rolls, withdifferent elastomeric compositions in each, can also be used to depositthese elastomeric compositions in different portions of the element.Gravure printing process includes direct and indirect (or off-set)methods. The direct gravure printing process deposits the elastomericcomposition directly onto the substrate. The indirect or off-set gravureprinting process first deposits the elastomeric composition onto anoffset roll or a carrier surface and then transfers it to the substrate.In the indirect process, the elastomeric composition may be partiallycooled and even partially solidified when it finally contacts thesubstrate. Moreover, the off-set gravure printing process provides awider temperature range for the process, even when a low thermalstability substrate is used.

In some embodiments, the non-contact spraying method is used. Thesuitable spraying equipment may include multiple nozzles arranged inseries or in parallel. Multiple nozzles can be arranged in an arrayalong the machine direction, along the cross machine direction, at anangle with respect to either direction, or combinations thereof. Thenozzles may apply the same or different elastomeric compositions and mayhave same or different sizes of orifice to apply different amounts ofthe elastomeric compositions to different areas of the substrate.Further, these nozzles may be controlled so that they start and stopindependently and at well defined times to give any desired stretchproperty in any given area. A suitable spraying equipment is UFD Omega,available from ITW Dynatec, Hendersonville, Tenn.

Furthermore, it is also possible to combine different depositionprocesses, for example gravure printing with spraying, to obtain thedesired properties in the resulting stretch composites.

The local stretch property can be varied in different ways. It can bevaried discretely in which the property changes in a stepwise manner. Anexample of such stepwise change would be to apply a high performanceelastomer in one portion of an element of the diaper (such as the toppart of an ear portion) and a lower performance elastomer in anotherportion of that element (such as the lower part of the ear portion)where the stretch requirements are less demanding. The stretch propertycan also be varied continuously, either linearly or non-linearly. Thecontinuous changes in stretch properties may be achieved by a gravurepattern designed in such a way that the cell depth decreases graduallyalong the circumference of the roll, thus resulting in a printed patternwhere the amount of deposited elastomeric composition decreasescontinuously in the machine direction.

The stretch composite can be manufactured by process 100 of the presentinvention, one embodiment of which is illustrated schematically inFIG. 1. Process 100 may include a primary operation of making acomposite preform which includes the steps of supplying a firstsubstrate; applying an elastomeric material to the first substrate; andoptionally joining with a second substrate. Process 100 may optionallyinclude a secondary operation of incrementally stretching the compositepreform to provide extensibility to the fibrous substrate.

The primary operation of process 100 is shown in details in FIG. 4, thefirst substrate 34 is provided by a first supply roll 52 and movesthrough an application device 105, shown here is a rotogravure printingdevice comprising a gravure printing roll 54 and a back-up roll 56, thatdeposits the elastomeric composition for elastomeric members ontosubstrate 34. The elastomeric composition being in a fluid state, may atleast partially penetrate substrate 34 to provide a printed substrate35, resulting in direct bonding between the elastomeric members and thesubstrate. Optionally, a second substrate 36 may be provided by a secondsupply roll 62 and combined with the printed substrate 35 via nip rolls64, 66 to sandwich the elastomeric members between substrates 34, 36 toform a composite preform 37. If necessary, adhesives may be used to bondthe elastomeric members and the second substrate. At this point of theprocess, a zero strain laminate is produced wherein the elastomericmembers and the substrates are bonded in an unstrained state.

The printed substrate 35 and/or the composite preform 37 may besubjected to additional treatments such as drying, cooling,consolidating (e.g., passing between a pair of nip rolls), crosslinking,and/or curing (e.g., via chemical, thermal, radiation methods) toenhance the elastic and mechanical properties of the elastomericcomposition deposited thereon and of the resulting composite preform.

An optional, secondary operation of process 100 uses forming station 106to incremental stretch the composite preform 37 to the extent that thesubstrate is permanently elongated and composite preform 37 is convertedinto stretch composite 108. Due to this structural change, the substratehas a reduced resistance to stretch and the elastomeric members are ableto stretch to the extent provided by the permanent elongation of thesubstrate.

Alternatively, pre-straining of substrates 34 and/or 36 prior to beingused in process 100 may impart extensibility to the substrates andenable the elastomeric members in the stretch composite to stretch tothe ultimate elongation of the substrate.

A process sometimes referred to as “ring-rolling,” may be a desirableincremental stretching operation of the present invention. In the ringrolling process, corrugated interengaging rolls are used to permanentlyelongate the fibrous substrate to reduce its resistance to stretch. Theresulting composite has a greater degree of stretchability in theportions that have been subjected to the ring rolling process. Thus,this secondary operation provides additional flexibility in achievingstretch properties in localized portions of the stretch composite.

Methods for imparting stretchability to an extensible or otherwisesubstantially inelastic material by using corrugated interengaging rollswhich incrementally stretch in the machine or cross-machine directionand permanently deform the material are disclosed in U.S. Pat. No.4,116,892, issued on Sep. 26, 1978, to E. C. A. Schwarz; U.S. Pat. No.4,834,741, issued on May 30, 1989, to R. N. Sabee; U.S. Pat. No.5,143,679, issued on Sep. 1, 1992 to G. M. Weber et al.; U.S. Pat. No.5,156,793, issued on Oct. 20, 1992, to K. B. Buell et al.; U.S. Pat. No.5,167,897, issued on Dec. 1, 1992 to G. M. Webber et al.; and U.S. Pat.No. 5,422,172, issued on Jun. 6, 1995, to P. C. Wu; and U.S. Pat. No.5,518,801, issued on May 21, 1996 to C. W. Chappell et al. In someembodiments, the composite preform may be fed into the corrugatedinterengaging rolls at an angle with respect to the machine direction ofthis secondary operation. Alternatively, the secondary operation mayemploy a pair of interengaging grooved plates applied to the compositepreform under pressure to achieve incremental stretching of thecomposite preform in localized portions.

It is desirable that the extensible substrate does not exhibitresistance to stretch when the composite is subjected to a typicalstrain under the in-use condition. The in-use strains experienced by thecomposite is due to the stretching when the article is applied to orremoved from a wearer and when the article is being worn. The extensiblesubstrate can be pre-strained to impart the desired stretchability tothe composite. Typically, when the extensible substrate is pre-strainedto about 1.5 time of the maximum in-use strain (typically less thanabout 250% strain), the extensible substrate becomes permanentlyelongated such that it does not exhibit resistance to stretch within therange of in-use strain and the elastic properties of the composite issubstantially the same as the total properties of the elastomericmembers in the composite.

The stretch composite may have an directional elasticity in at least onedirection of less than about 400 N/m, preferably from about 5 N/m toabout 400 N/m, more preferably from about 25 N/m to about 300 N/m, andmost preferably from about 75 N/m to about 200 N/m, when measured asload at 75% strain. Additionally, the resulting stretch composite hasthe following properties: a directional percent set in at least onedirection of less than about 20%, preferably less than about 15% andmore preferably less than about 10%; and a directional stress relaxationvalue in at least one direction of less than about 30%, preferably lessthan about 22%, and more preferably less than about 15%.

In one embodiment, as shown in FIG. 1, the ring rolling process isincorporated into process 100 as a secondary operation, which includes aforming station 106 positioned between application device 105 andtake-up roll 70. Alternatively, if a second substrate 36 is included,the forming station 106 may be positioned between the second supply roll62 and the take-up roll 46. Referring to FIG. 5, composite preform 37 isfed to the nip 107 formed by a pair of opposed forming rolls 108 and 109that together define a forming station 106. Forming station 106incrementally stretch and permanently elongates the substrate, therebycomposite preform 37 is converted into stretch composite 38.

Exemplary structures and relative positions of forming rolls 108, 109are shown in an enlarged perspective view in FIG. 6. As shown, rolls 108and 109 are carried on respective rotatable shafts 121, 123, havingtheir axes of rotation disposed in parallel relationship. Each of rolls108 and 109 includes a plurality of axially-spaced, side-by-side,circumferentially-extending, equally-configured teeth 122 that can be inthe form of thin fins of substantially rectangular cross section, orthey can have a triangular or an inverted V-shape when viewed in crosssection. The outermost tips of the teeth are preferably rounded to avoidcuts or tears in the materials that pass between the rolls.

The spaces between adjacent teeth 122 define recessed,circumferentially-extending, equally configured grooves 124. The groovescan be of substantially rectangular cross section when the teeth are ofsubstantially rectangular cross section, and they can be of invertedtriangular cross section when the teeth are of triangular cross section.Thus, each of forming rolls 108 and 109 includes a plurality of spacedteeth 122 and alternating grooves 124 between each pair of adjacentteeth. The teeth and the grooves need not each be of the same width,however, and preferably the grooves have a larger width than that of theteeth, to permit the material that passes between the interengaged rollsto be received within the respective grooves and to be locallystretched, as will be explained hereinafter.

FIG. 7 is an enlarged view of several interengaged teeth 122 and grooves124 with a composite preform being modified therebetween. As shown, aportion of composite preform 37, is received between the interengagedteeth and grooves of the respective rolls. The interengagement of theteeth and grooves of the rolls causes laterally spaced portions ofcomposite preform 37 to be pressed by teeth 122 into opposed grooves124. In the course of passing between the forming rolls, the forces ofteeth 122 pressing composite preform 37 into opposed grooves 124 imposewithin composite preform 37 tensile stresses that act in the cross-webdirection. The tensile stresses cause intermediate portions 126 that liebetween and that span the spaces between the tip portions 128 ofadjacent teeth 122 to stretch or extend in a cross-web direction, whichresults in a localized reduction of the web thickness as well as webtensile strength at each of intermediate portions 126.

The action of pressing of portions of composite preform 37 into therespective grooves 124 by teeth 122 therefore causes a non-uniformreduction of the thickness of composite preform 37 to take place in thecross-web direction of the composite. The thickness of portions tip thatare in contact with the tooth tips reduces only slightly, comparing tothe thickness reduction of intermediate portions 126 that span adjacentteeth 122. Thus, by passing through the interengaged rolls and beinglocally laterally stretched at spaced intervals between adjacent teeth,the inelastic elongatable or extensible fibrous web develops alternatinghigh and low basis weight regions. The low basis weight regions arefound at the positions of the web wherein the web material has beenlocally laterally stretched. Additional cross-web stretching of theexiting, formed web can be effected by passing the modified web betweenso-called Mount Hope rolls, tentering frames, angled idlers, anglednips, and the like, each of which is known to those skilled in the art.

Alternatively, other process embodiments of the present invention caninclude the use of multiple deposition devices to provide multipledepositions of elastomeric materials onto one or more substrates,including deposition onto two substrates separately and then combingthem, and/or making several subsequent depositions onto the samesubstrate. Further, the use of multiple deposition devices can provide agreater deposition weight of the elastomeric material, a greater zdimension profile variation, capability to deposit different elastomericmaterials, and capability to deposit elastomeric materials of differentcolors, and any combinations thereof

In one embodiment, the outer cover 40 of a pant type diaper 20 shown inFIG. 2A may include chassis elastomeric members 26 to provide desiredbreathability of the outer cover 40 while maintaining liquidimpermeability of the outer cover 40. Chassis elastomeric members 26 maybe disposed on either side of the outer cover 40 in the tummy region,the buttocks region or the crotch region. Multiple chassis elastomericmembers 26 may be disposed on the outer cover 40 with variousorientations. For example, multiple chassis elastomeric members 26 maybe disposed parallel to, perpendicular to, or at an angle to the waistregion or the leg openings, and each elastomeric member may havedifferent orientation from neighboring elastomeric members.

TEST METHODS

Melt Viscosity Test

Melt viscosity of elastomeric compositions which comprise theelastomeric members can be measured using the RDA II Viscometer(manufactured by Rheometrics) or the AR 1000 Viscometer (manufactured byTA Instruments) in the parallel plate mode. Calibration, sample handlingand operation of the instrument follow the manufacturer's operatingmanual generally. Testing conditions used specifically for this test aredisclosed herein. In this test, the sample is placed between twoparallel plates that are 25 mm in diameter and have a gap of 1.5 mmbetween them. The sample chamber is heated to and maintained at 175° C.Melt viscosity is measured under the steady state condition at shearrate of 1 s⁻¹ and an oscillation of 5% strain.

Hysteresis Test for Elastic Properties

(i) Sample Preparation for The Elastomeric Member

The properties of the elastomeric members are obtained using testsamples made cast films. About 5 grams of the elastomeric composition,which makes up the elastomeric members, is sandwiched between twosilicone-coated release films and is heated to about 150 to 200° C. andpressed in a Carver hand press under sufficient pressure for one minuteto consolidate the elastomeric composition. Then, the pressure isreleased and the film is allowed to cool down. Depending on the type ofelastomeric composition being cast, temperatures and pressures can beadjusted accordingly. Shims of 0.010″ (0.254 mm) thickness are used toobtain uniform film thickness. Test samples of specific sizes for agiven test and /or instrument are cut and trimmed from the cast film.For example, samples used herein are 1″ by 3″ (25.4 mm by 76.2 mm). Allsurfaces of the sample should be free of visible flaws, holes, scratchesor imperfections.

(ii) Sample Preparation for The Composite

Samples of 1″ by 3″ (25.4 mm by 76.2 mm) size are obtained from theelasticized region of the composite. It is recognized that the stretchcomposite may exhibit directional properties that are not the same whenthe composite is measured in different directions, depending on theorientation of the elastomeric members within the sample. Therefore,samples from a given elasticized region are prepared with four differentorientations in order to obtain representative directional properties ofthe composite. Specifically, the samples are obtained from a givenelasticized region with its longitudinal axis aligned in a firstdirection, a second direction which is perpendicular to the firstdirection, and a third and a forth directions which are +/−45 withrespect to the first direction. The first direction may be, but is notrequired to be, the machine direction (i.e., the substrate movementdirection during the process of applying the elastomeric members to thesubstrate). At least three samples along each orientation are prepared.Where the composite is substantially homogenous to the naked eyes, thesedirectional samples can be taken from neighboring elasticized regions.Where the composite is visibly inhomogenous from one region to another,these directional samples can be taken from the same elasticized regionfrom multiple pieces of the same composite material (e.g., threereplicate directional samples may be obtained from the same stretchcomposite material found on three diapers). Typically, the chosenelasticized region is visually identified as the region having thehighest density of elastomeric members. It is typical, though notrequired, to test more than one elasticized regions to fullycharacterize the directional properties of the composite. Care should betaken that the three replicate samples are similar to one another. Ifthe elasticized region is not large enough to provide these 1″ by 3″(25.4 mm by 76.2 mm) samples, the largest possible sample size is usedfor testing, and the test method is adjusted accordingly. All surfacesof the sample should be free of visible flaws, scratches orimperfections.

(iii) The Hysteresis Test For The Elastomeric Members

A commercial tensile tester from Instron Engineering Corp., Canton,Mass. or SINTECH-MTS Systems Corporation, Eden Prairie, Minn. may beused for this test. The instrument is interfaced with a computer forcontrolling the test speed and other test parameters, and forcollecting, calculating and reporting the data. The hysteresis ismeasured under typical laboratory conditions (i.e., room temperature ofabout 20 C. and relative humidity of about 50%).

The procedure is as follows:

-   -   (1) choose appropriate jaws and load cell for the test; the jaws        should be wide enough to fit the sample, typically 1″ wide jaws        are used; the load cell is chosen so that the tensile response        from the sample tested will be between 25% and 75% of the        capacity of the load cells or the load range used, typically a        50 lb load cell is used;    -   (2) calibrate the instrument according to the manufacturer's        instructions;    -   (3) set the gauge length at 1″ (25.4 mm);    -   (4) place the sample in the flat surface of the jaws such that        the longitudinal axis of the sample is substantially parallel to        the gauge length direction;    -   (5) set the cross head speed at a constant speed of 10″/min        (0.254 m/min) until it reaches 112% strain; then return to the        original gauge length at 10″/min (0.254 m/min); and at the end        of this pre-straining cycle, start timing the experiment using a        stop watch;    -   (6) reclamp the pre-strained sample to remove any slack and        still maintain a 1″(25.4 mm) gauge length;    -   (7) at the three minute mark on the stop watch, start the        hysteresis test and the instrument records load versus strain        data simultaneously; the hysteresis test has the following        steps:    -    a) go to 75% strain at a constant rate of 10″/min (0.254        m/min);    -    b) hold for 2 minutes;    -    c) return to 0% strain at a constant rate of 10″/min (0.254        m/min);    -    d) hold for 1 minute; and    -    e) go to 0.1 N at a constant rate of 2″/min (50.8 mm/min). From        the data collected in step 7(a), the elasticity is determined        from the load at 75% strain, which is normalized to 85 grams per        square meter (gsm) as follows: the load at 200% strain from the        plot is divided by the width of the sample, then multiplied by a        normalizing factor, which is 85/(½* (actual weight of the        sample/(width * gauge length) of sample in m²)), or 85/(½*        (actual weight of the sample)/(6.47×10⁻⁴)) if the sample        dimension is measured in inches. From the data collected in step        7(e), the % set is determined from the strain at 0.1 N, which is        a force deemed sufficient to remove the slack but low enough to        impart, at most, insubstantial stretch to the sample.

From the data collected in step 7(b), the force relaxation is determinedby the load at the beginning and at the end of the 2 minutes hold timeusing the following formula:${\%\quad{Force}\quad{Relaxation}\quad{at}\quad{time}},{t = {\frac{\left\lbrack {\left( {{initial}\quad{load}} \right) - \left( {{{load}\quad{at}\quad{time}},t} \right)} \right\rbrack}{\left( {{initial}\quad{load}} \right)} \times 100}}$

For the elastomeric members, the average results from three replicatesamples are reported.

(iv) The Hysteresis Test For The Elastomeric Composites

There is no pre-straining of the composite sample in this hysteresistest and the load at 75% strain is normalized to 85 gsm of the compositebasis weight. In this test, steps 1-4 are performed as above; at the endof step 4, there is a one minute holding at 0%strain; and steps 7(a-e)immediately follow.

The elastic properties are obtained from the recorded data as above, andthe load at 75% strain is normalized to 85 gsm basis weight of thecomposite and is reported as such. For the elastomeric composites, theaverage results from three replicate samples in each direction arereported as “directional elasticity”, “directional % set” and“directional stress relaxation”.

EXAMPLES Example 1

A phase change solvent having the general structure (I) is prepared bycombining 260 grams (2 moles) of octanol with 404 grams (2 moles) ofterephthaloyl chloride and 202 grams (1 mole) of 1,12-dodecanediol in1500 ml of chloroform in a reaction flask. The mixture is allowed toreact at 55° C. for 20 hours with constant stirring and under a vacuum,which removes HCl generated by the reaction. The reaction is terminatedby cooling the mixture to room temperature. The resulting reactionmixture is poured into a large quantity of methanol to precipitate theproduct. The precipitant is collected over a filter, washed with 500 mlof methanol 3 times and dried at 45° C. in an vacuum oven for 20 hours.

An elastomeric composition is prepared by mixing and stirring this phasechange solvent and SEPTON® S4033 (available from Kuraray America, Inc.,New York, N.Y.) at 120° C. for 4 hours or until the sample appears to behomogeneous. The mixture is cooled to room temperature. Mineral oil,DRAKEOL® Supreme (available from Pennzoil Co., Penrenco Div., KarnsCity, Pa.) is then added to the mixture and stirred at room temperaturefor 16-24 hours to form an elastomeric composition. For this example,the final elastomeric composition contains 40 wt% SEPTON® S4033, 30 wt%crystalline solvent and 30 wt% mineral oil. This elastomeric compositionhas a melt viscosity of about 24 Pa·s at 175° C. and 1 s⁻¹.

The above blending method is merely exemplary. Other conventionalblending methods using batch mixers, screw extruders, and the like, canalso be used.

Example 2

The elastomeric composition of Example 1 is processed through a directgravure system (available from Roto-therm Inc., Redding Calif.) at atemperature of about 175° C. The direct gravure system includes a tank,a bath, hoses, a patterned steel roll (i.e., the gravure roll) and aback-up roll. The tank holds the elastomeric composition; the tank isconnected the hoses which serve as the conduits for transporting theelastomeric composition to the bath. All these components are heated toabout 175° C. so that the elastomeric composition is maintained at afairly constant temperature during the printing process. The gravureroll is 9.3″ (0.236 m) in diameter and is also heated to about 175° C.The gravure roll has grooves and lands on its surface for depositing theelastomeric composition onto a substrate in a continuous trihelicalpattern not shown in FIG. 4. The grooves are 0.020″ (0.51 mm) wide and0.0075″ (0.19 mm) deep and the land width is 0.023″ (0.58 mm). Totalwidth of the pattern on the gravure roll is 5″ (0.127 m). The back-uproll is 6.25″ (0.158 m) in diameter and is made of silicone rubber tohave a hardness of 55 Shore A. The substrate is a HEC polypropylenenonwoven web (available from BBA Nonwovens Inc. of S.C.) having a basisweight of about 22 grams per square meter.

Referring to FIG. 4, a substrate 34 is unwound from a first supply roll52 and is fed between the gravure printing roll 54 and the back-up roll56, both operating at a line speed of 50-200 feet per minute and providea nip pressure of 6-12 mm. Nip pressure was quantified in terms of afootprint, which is the impression that the rubber roll makes on thesteel cylinder. Footprint can vary from about 3 mm to 24 mm using thisequipment. Proper nip pressure is chosen to effectuate the transfer ofthe composition from the gravure roll to the substrate and to controlthe penetration of the composition into the substrate. Transferefficiency, which is the fraction of the cells that are emptied,typically ranged from about 40-60%. The gravure printing roll 54 picksup the elastomeric composition from the heated bath (not shown) andtransfer it directly to the substrate to form a printed substrate 35. Asecond substrate 36, which is the same nonwoven web as the firstsubstrate 34, is unwound from a second supply roll 62 and combined withthe printed substrate 35 between two rubber nip rolls 64, 66, therebyforming the composite preform 37. Nip pressure, temperature, and contacttime can be adjusted to give optimum bonding.

The composite preform is subjected to incremental stretching in one ormore portions by pressing said portions between two interengaginggrooved plates, one stationary and the other movable. The plates are atleast 4″×4 ″ in dimension and are made of stainless steel. The pitch,which is the distance between adjacent teeth on a plate, is 1.524 mm;the tooth height is 10.31 mm; the tooth tip radius is 0.102 mm; and thedepth of engagement (DOE), which is the distance between two adjacenttooth tips from two teeth on opposed, interengaging plates that controlshow deeply the teeth are engaged, is 3.639 mm.

The composite preform is placed on the stationary plate; the movableplate approaches and engages with the stationary plate at a speed of1.82 m/s. Upon reaching the desired DOE, the movable plate reverses andreturns to its original position. Thus, by varying the portion and/orthe direction the composite preform placed in between the grooved platesand/or by varying the DOE, the resulting composite can have incrementalstretching to a varying extent, in any portion thereof and in anyorientation.

Example 3

The process is similar to that of Example 2, except an off-set gravureprinting process is used. The elastomeric composition is firsttransferred from the gravure printing roll to a silicone release paper(available from Waytek Corporation, Springboro, Ohio) and then substrate34 is nipped in between an additional set of rubber rolls to getcomplete transfer from the release paper to the substrate. Since theserubber rolls are not heated, the elastomeric composition is cooledduring this off-set printing step such that it contacts the substrate ata temperature lower than the processing temperature of 175° C. Thus,there is a reduced likelihood of thermal damages to the delicatestructure of the nonwoven substrate.

COMPARATIVE EXAMPLES

Comparative examples are made from blends of SEPTON® S4033, mineral oil,DRAKEOL® Supreme, and VECTOR® 4211 (available from Dexco ChemicalCompany, Houston , Tex.). The blends can be prepared by the methodsdescribed in Example 1 or any conventional blending methods .Comparative example 1 is a blend of 60 wt% VECTOR® 4211 and 40 wt%mineral oil. Comparative example 2 is a blend of 55 wt% VECTOR® 4211 and45 wt% mineral oil. Comparative example 3 is a blend of 30 wt% SEPTON®S4033 and 70 wt% mineral oil. Comparative example 4 is a blend of 35 wt%SEPTON® S4033 and 65 wt% mineral oil. Comparative example 5 is a blendof 40 wt% SEPTON® S4033 and 60 wt% mineral oil. Comparative example 6 isa hot melt adhesive H2737, available from Bostik Findley, Middletown,Mass. Comparative example 7 is a metallocene-catalyzed polyethyleneENGAGE® ENR 8407, available from Dow Chemical Company of Midland, Mich.

Film samples of the comparative examples and Example 1 of the presentinvention are prepared and subjected to the hysteresis test describedabove. The results are reported below. TABLE 1 Melt Force ViscosityNormalized Relaxation Basis (175° C., * Load at (75%, 2 min., Weight. 1s⁻¹) 75% Strain room temp.) % set (gsm) (Pa s) (N/m) (%) (%) Example 1198 24 99.40 19.8 3.7 Comparative Examples 1 158 630 12.76 8.1 6.8 2 224484 13.75 5.4 5.0 3 232 21 14.52 8.7 6.1 4 225 40 18.78 7.9 4.6 5 141203 25.15 6.8 4.6 6 200 7 14.50 7.4 5.0 7 175 490 190.55 24.9 6.8* Normalized to a basis weight of 85 grams per square meter.

TABLE 1 shows that most comparative examples do not have the desiredmelt viscosity suitable for the controlled deposition processes usedherein to produce the stretch composites. Further, for those comparativeexamples that have a suitably low melt viscosity, they exhibit asubstantial trade-off in properties, resulting in unsatisfactory elasticproperties. Example 1 of the present invention uniquely provides thedesired melt viscosity suitable for the processes used herein withoutcompromising the elastic properties.

The dimensions and values disclosed herein are not to be understood asbeing strictly limited to the exact numerical values recited. Instead,unless otherwise specified, each such dimension is intended to mean boththe recited value and a functionally equivalent range surrounding thevalue. For example, a dimension disclosed as “40 mm” is intended to mean“about 40 mm”.

All documents cited in the Detailed Description of the Invention are, inrelevant part, incorporated herein by reference, the citation of anydocument is not to be construed as an admission that it is prior artwith respect to the present invention. To the extent that any meaning ordefinition of a term in this written document conflicts with any meaningor definition of the term in a document incorporated by reference, themeaning or definition assigned to the term in this written documentshall govern.

While particular embodiments of the present invention have beenillustrated and described, it would be obvious to those skilled in theart that various other changes and modifications can be made withoutdeparting from the spirit and scope of the invention. It is thereforeintended to cover in the appended claims all such changes andmodifications that are within the scope of this invention.

1. A process for making a stretch composite from an extensiblesubstrate, said process comprising the steps of: a. providing a firstextensible substrate; b. providing an application device, said deviceincluding at least one patterned print roll; c. printing one or moreelastomeric compositions by means of said patterned print roll, saidcompositions having a melt viscosity of from about 1 to about 150 Pa·s,measured at 175° C. and 1 s⁻¹ strain rate, an elasticity of at leastabout 50 N/m at 20° C., and a stress relaxation of less than about 20%,onto said substrate thereby forming one or more intermediate structures;and d. incrementally stretching one or more portions of the intermediatestructures to permanently elongate the substrate in the portions.
 2. Theprocess of claim 1 wherein said process further comprises after printinga step of converting the elastomeric compositions into elastomericmembers.
 3. The process of claim 2 wherein the converting comprises oneor more processes selected from the group consisting of crosslinking,curing, cooling, pressing, and combinations thereof.
 4. The process ofclaim 1 wherein the elastomeric compositions have a percent set of lessthan about 20%.
 5. The process of claim 4 wherein the thermoplasticelastomer is selected form the group consisting of styrenic blockcopolymers, metallocene-catalyzed polyolefins, polyesters,polyurethanes, polyether amides, and combinations thereof; and the phasechange solvent has the following formula: (I)R′-L_(y)-(Q-L_(x))_(n−1)-Q-L_(y)-R; (II) R′-L_(y)-(Q-L_(x))_(n)-R; (III)R′-(Q-L_(x))_(n)-R; (IV) R′-(Q-L_(x))_(n−1)-Q-L_(y)-R; (V)R′-(Q-L_(x))_(n−1)-Q-R; or a mixture thereof; wherein Q may be asubstituted or unsubstituted difunctional aromatic moiety; L is CH₂; Rand R′ are the same or different and are independently selected from H,CH3, COOH, CONHR₁, CONR₁R₂, NHR₃, NR₃R₄, hydroxy, or C1—C30 alkoxy;wherein R₁, R₂, R₃ and R₄ are the same or different and areindependently selected from H or linear or branched alkyl from C1—C30; xis an integer from 1 to 30; y is an integer from 1 to 30; and n is aninteger from 1 to
 7. 6. The process of claim 1 wherein the incrementallystretched portion of the stretch composite exhibits the followingproperties in at least one direction: a directional elasticity of fromabout 5 N/m to about 400 N/m; a directional percent set of less thanabout 20%; and a directional stress relaxation of less than about 30%after 2 minutes at room temperature and 75% strain.
 7. The process ofclaim 1 wherein the composite comprises one or more elasticized regionsof an absorbent article.
 8. The process of claim 7 wherein the one ormore elasticized regions of the absorbent article is selected from thegroup consisting of an elasticized waist region, an elasticized cuffregion, an elasticized side panel, an elastic ear portion, anelasticized outercover, an elasticized topsheet, a fastener system, andcombinations thereof.
 9. The process of claim 1 wherein prior toincremental stretching said process further comprises a step oflaminating a second substrate to the first extensible substrate with theone or more elastomeric members sandwiched between the first and secondsubstrates.
 10. The process of claim 2 wherein the elastomeric membersare different in a characteristic selected from the group consisting ofcompositions, add-on levels, shape, pattern, and combinations thereof.11. The process of claim 2 wherein the elastomeric members arerectilinear or curvilinear, and at least two of the elastomeric membersare non-parallel with respect to each other.
 12. The process of claim 7wherein the one or more elasticized regions are adjacent or at leastpartially overlapping.